BACKSCATTERED ELECTRON IMAGING OF THE CALCIFIED TISSUES PRESENT IN BONE HEALING

The aspect of calcified tissues involved in fracture healing was studi ed by means of backscattered electron imaging. Bilateral transverse mi dshaft osteotomies were performed in the tibiae of 16 dogs. The osteot omies were reduced by means of a type II external skeletal fixator, an d the clinical and radiographic course was assessed weekly until the m oment of euthanasia, one, two, four and eight weeks after the operatio ns. The osteotomized areas were removed and their structure examined i n the scanning electron microscope, using backscattered electron image s, to determine the general aspect of the extracellular matrix of the calcified tissues present. Four different tissues were observed: lamel lar bone, woven bone, calcified cartilage and chondroid tissue. The ba ckscattered electron contrast and fibre arrangement of the matrix, as well as the size and shape of the cellular lacunae, allow identificati on of the tissue. Chondroid tissue, which seems to have a leading role in the early phases of fracture healing, shows a characteristic patte rn of a highly calcified and fibrous matrix with a large number of irr egular and confluent cell lacunae.